[time-nuts] Lost GPS lock or 1PPS recently?

Fri Sep 7 01:08:21 UTC 2018

As to eLORAN,  you can deny positioning but maintain timing service simply by modifying the GRI and since eLORAN is software based thats not a difficult change.

Navigation receivers go into fail but timing receivers only need ONE station.   As the users of SRS700’s and Austrons do when Wildwood is active.

With GNSS its a hell of a lot harder and without SA your only option is to turn off all the C/A signals hence denying civillian use of GNSS

I’m pretty sure if a non-state actor was doing weaponized drone attacks with GPS for guidance,  GPS for civilian use would be shut down in a NY minute .

Remember govt users would not be affected as they have access to the PPS and the ‘word of the day’ to make it active.

You dont need conspiracies to think of conditions where GPS would be shut down for long periods of time and where reasonable people would agree with the shutdown.

On Sep 6, 2018, at 8:44 PM, Scott McGrath <scmcgrath at gmail.com> wrote:

Gee,  thats strange especially for those of us who ran the Austron comparitors to check our local standards against the LORSTA’s

On Sep 6, 2018, at 8:04 PM, Bob kb8tq <kb8tq at n1k.org> wrote:

Hi

No, eLoran *never* on it’s best day could ever deliver the kind of timing that the vast majority
of these systems require. It simply is not and can not do the job. The world has moved *way*
past the sort of timing it can actually deliver. 

Bob

> On Sep 6, 2018, at 6:35 PM, Scott McGrath <scmcgrath at gmail.com> wrote:
> 
> Actually we DID have a radio based system that provided sufficient accuracy it was called eLORAN but it was killed by US politicians because they did not want a much more inexpensive to operate system ‘competing’ with GPS.    Shutting down LORAN saved 32m dollars annually the NAVSTAR GPS program costs billions annually.
> 
> Ironically while LORAN’s absolute accuracy is less than GPS,  repeatability was much better so fishermen liked LORAN better.
> 
> Once again the empty suits won and the navigation and timing community lost.
> 
> Wrt cellsites staying operational i imagine the oscillators in holdover would probably remain sufficiently synchronized for a month or so.
> 
> 
> 
> On Sep 6, 2018, at 4:56 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
> 
> Hi
> 
> Well, we *do* have experience with that. It was called selective availability. Indeed it might get turned back on again. It’s impact on a properly designed GPSDO - not much. It takes a bit longer to get to best stability. System time wise, it still works “good enough”. 
> 
> A four hour long test format also does basically nothing to a GPSDO based system. You didn’t read anything in the papers about all cell service in three states going away. The devices did what they are supposed to do and everything did it’s boringly normal thing ….. it worked fine. 
> 
> I still don’t quite understand just what people think could replace satellite based timing in these systems. None of the “radio based” systems are within a factor many thousands to a few million of being adequate. 
> 
> =====
> 
> Now, if this is headed off into a “the government is coming to break down the doors and take away all my toys sort of thing. That’s very much *not* a Time Nuts topic.
> 
> Bob
> 
>> On Sep 6, 2018, at 11:34 AM, Scott McGrath <scmcgrath at gmail.com> wrote:
>> 
>> And there is the other significant vulnerability since GPS is a MILITARY system the DoD can take it offline for any reason at any time.  
>> 
>> Leaving civilian users with nothing, 
>> 
>> If its a national security threat its likely the other GNSS systems will be unavailable as well.
>> 
>> 
>> 
>> 
>> 
>> On Sep 6, 2018, at 9:53 AM, John Sloan <jsloan at diag.com> wrote:
>> 
>> 
>> Folks:
>> 
>> Well blow me down. It took some Google Maps fu on the web on my part, but
>> my time and place does indeed coincide with this “GPS Interference Testing” at
>> White Sands Missile Range. I just happened to be in my home office watching
>> several of my GPS-disciplined NTP servers when this occurred. Thanks, Graham!
>> 
>> :John
>> 
>>> ZDV   DENVER (ARTCC),CO. [Back to Top] !GPS 08/260 (KZDV A0287/18) ZDV NAV
>>> GPS (WSMR GPS 18-20) (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT BE AVBL WI A
>>> 359NM RADIUS CENTERED AT 333345N1063840W (TCS054036) FL400-UNL, 311NM
>>> RADIUS AT FL250, 215NM RADIUS AT 10000FT, 223NM RADIUS AT 4000FT AGL, 169NM
>>> RADIUS AT 50FT AGL DLY 1830-2230 1809031830-1809082230
>> 
>> --
>> J. L. Sloan            Digital Aggregates Corp.
>> +1 303 940 9064 (O)    3440 Youngfield St. #209
>> +1 303 489 5178 (M)    Wheat Ridge CO 80033 USA
>> jsloan at diag.com        http://www.diag.com <http://www.diag.com/>
>> 
>> 
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